Evaluate: `int n. x^(n-1) ." cos " x^(n) " dx "`

Explanation

To evaluate the integral \( \int n \cdot x^{n-1} \cdot \cos(x^n) \, dx \), we can follow these steps:

### Step 1: Substitution
Let \( t = x^n \). Then, we differentiate both sides to find \( dt \):
\[ dt = n \cdot x^{n-1} \, dx \]
This implies:
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